Semiconductor metal-oxide-

The addition of a second species can cause a decrease in charge recombination and an increase in the TiOz photocatalytic efficiency. Such behavior was examined by loading a series of species on the surface or into the crystal lattice of photocatalysts inorganic ions [148-152], noble metals [153,154], and other semiconductor metal oxides [155], It was thus proven that modifications produced by these species can change semiconductor surface properties by altering interfacial electron-transfer events and thus the photocatalytic efficiency. 

Table 5-6 shows for semiconductor metal oxides the flat band potential in aqueous solutions at various pH values and the conduction band edge potential E c at the iso-electric point pH,. ... 

The inherent electronic nature of semiconductor metal oxides can direcdy interact with molecular excited states in a manner not energetically possible with insulators. More specifically, an excited sensitizer, S, may transfer an electron to the semiconductor forming a charge separated pair [Eq. (1)] ... 

Metals, semiconductors, metal oxides, carbon, polymers... 

As summarized in Table 2 base metal oxides can be classified into three groups /7-type semiconductors, -type semiconductors, and insulators, the catalytic activity of which for CO oxidation decreases in this order. As support for Pt group metals, except for Au, semiconductor metal oxides are more effective than insulating metal oxides because the former are partly reducible by CO and H2 at temperatures below 200 °C. However, the degree of reducibility is not directly reflected on the support effect. Although n-type semiconductor metal oxides themselves are less active than /7-type semiconductor ones, their support effect is usually larger. The reason is not clear. However, it seems to be curious that noble metals supported on /7-type semiconductors have not been extensively studied so far, except for a few cases. 

The view that POMs might represent molecular versions of semiconductor metal oxide particles has been addressed repeatedly by several groups.301,389,394 While POMs and colloidal semiconductor metal oxide particles have some features in common, some features of the both the excited states and the reduced ground states resulting from photoredox chemistry of the two types of clusters are clearly distinct. 

Marquis, B.T. and Vetelino, J.R, A semiconductor metal oxide sensor array for the... 

The most common photocatalytic processes, in terms of both mechanistic analysis and practical use, involve insoluble semiconductor metal oxides or sulfides, which upon irradiation undergo dual interfacial electron transfer between the excited semiconductor surface and adsorbed donor (D) and/or acceptor (A) molecules (Scheme 6.291). Titanium dioxide (Ti02) is a particularly popular photocatalyst due to its good redox properties (see also Special Topic 6.29), high stability, low toxicity and low price. 

MBE MEIS MESFET MINDO MIS MOCVD MOMBE MOS MOSFET MOVPE molecular beam epitaxy medium energy ion scattering metal semiconductor field effect transistor modified intermediate neglect of differential overlap metal-insulator-semiconductor metal-organic chemical vapour deposition metal-organic molecular beam epitaxy metal-oxide-semiconductor metal-oxide-semiconductor field effect transistor metal-organic vapour phase epitaxy... 

Our work and that of Tench (24) has shown that the electron transfer sites on these metal oxides (e.g., MgO and CaO) are selective and yet present in high surface concentration. Preliminary activation by thermal or photochemical oxide means is required, however. This means that these processes can be related to photon-induced electron transfer (60, 61, 62, 63, 64) in semiconductor metal oxides in that similar surface sites may be required (i.e., similar coordination geometries). 

Key words silicon micromachining, micro-hotplates, semiconductor, metal-oxide, field-effect, gas sensors, CMOS and SOI, nanowires, printing, polymeric, plastic. 

Fermi level can reach in the semiconductor is the flat band potential Vfb which, in the case shown, is lower with respect to the H /Ha redox couple. This means that hydrogen evolution cannot take place at the metal electrode even at the highest irradiation intensity. For hydrogen evolution to occur, a positive bias must be applied to the semiconductor electrode as shown in Fig. 3d. This bias, which is usually provided by an external voltage source, should also account for the necessary cathodic and anodic ( 7a) overvoltages in order to sustain the current flow. This situation represents a condition which is frequently met with visible absorbing semiconductor metal oxides photochemically stable in aqueous environment, like WO3 orFejOa. 

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